You say that the last place team unloaded Oswalt... is this a keeper league where Oswalt cannot be kept by the last place team next year? If it is, then it is a very fair trade. If not, then that trade stinks but is still not vetoable.
Leagues should really have provisions in place to incentivize teams at the bottom to not give up or do shady things - in our league, we pay out the top 5 teams... then the 6th place team gets the 1st draft pick next year, 7th place gets the 2nd draft pick, down to the last place team who gets the 7th pick. Gives teams something to play for.
"The government cannot give to anyone anything that it does not first take from someone else"